Conventionally, substrates for use in a nitride semiconductor light-emitting element may include a GaN substrate, an SiC substrate, a sapphire substrate, and the like. Among those substrates, a sapphire substrate is widely used which has a predominance in price and mass productivity.
However, conventionally, there has been a problem of difficulty in growing a nitride semiconductor layer of GaN or the like on a sapphire substrate due to a lattice mismatching rate between the sapphire substrate and the nitride semiconductor layer of GaN or the like.
Therefore, for example, PTD 1 (Japanese Patent Laying-Open No. 6-196757) proposes a method of forming a low-temperature GaN buffer layer on a sapphire substrate and thereby growing a high-quality GaN layer on the low-temperature GaN buffer layer.